#ifndef Foundation_Buffer_INCLUDED
#define Foundation_Buffer_INCLUDED


#include "../Environment.h"
#include "../Debug/Assert.h"
#include "../Debug/Exception.h"
#include <cstring>
#include <cstddef>


namespace pi {


template <class T>
class Buffer
    /// A buffer class that allocates a buffer of a given type and size
    /// in the constructor and deallocates the buffer in the destructor.
    ///
    /// This class is useful everywhere where a temporary buffer
    /// is needed.
{
public:
    Buffer(std::size_t capacity):
        _capacity(capacity),
        _used(capacity),
        _ptr(0),
        _ownMem(true)
        /// Creates and allocates the Buffer.
    {
        if (capacity > 0)
        {
            _ptr = new T[capacity];
        }
    }

    Buffer(T* pMem, std::size_t length):
        _capacity(length),
        _used(length),
        _ptr(pMem),
        _ownMem(false)
        /// Creates the Buffer. Length argument specifies the length
        /// of the supplied memory pointed to by pMem in the number
        /// of elements of type T. Supplied pointer is considered
        /// blank and not owned by Buffer, so in this case Buffer
        /// only acts as a wrapper around externally supplied
        /// (and lifetime-managed) memory.
    {
    }

    Buffer(const T* pMem, std::size_t length):
        _capacity(length),
        _used(length),
        _ptr(0),
        _ownMem(true)
        /// Creates and allocates the Buffer; copies the contents of
        /// the supplied memory into the buffer. Length argument specifies
        /// the length of the supplied memory pointed to by pMem in the
        /// number of elements of type T.
    {
        if (_capacity > 0)
        {
            _ptr = new T[_capacity];
            std::memcpy(_ptr, pMem, _used * sizeof(T));
        }
    }

    Buffer(const Buffer& other):
        /// Copy constructor.
        _capacity(other._used),
        _used(other._used),
        _ptr(0),
        _ownMem(true)
    {
        if (_used)
        {
            _ptr = new T[_used];
            std::memcpy(_ptr, other._ptr, _used * sizeof(T));
        }
    }

    Buffer& operator = (const Buffer& other)
        /// Assignment operator.
    {
        if (this != &other)
        {
            Buffer tmp(other);
            swap(tmp);
        }

        return *this;
    }

    ~Buffer()
        /// Destroys the Buffer.
    {
        if (_ownMem) delete [] _ptr;
    }

    void resize(std::size_t newCapacity, bool preserveContent = true)
        /// Resizes the buffer capacity and size. If preserveContent is true,
        /// the content of the old buffer is copied over to the
        /// new buffer. The new capacity can be larger or smaller than
        /// the current one; if it is smaller, capacity will remain intact.
        /// Size will always be set to the new capacity.
        ///
        /// Buffers only wrapping externally owned storage can not be
        /// resized. If resize is attempted on those, IllegalAccessException
        /// is thrown.
    {
        if (!_ownMem) throw pi::InvalidAccessException("Cannot resize buffer which does not own its storage.");

        if (newCapacity > _capacity)
        {
            T* ptr = new T[newCapacity];
            if (preserveContent)
            {
                std::memcpy(ptr, _ptr, _used * sizeof(T));
            }
            delete [] _ptr;
            _ptr = ptr;
            _capacity = newCapacity;
        }

        _used = newCapacity;
    }

    void setCapacity(std::size_t newCapacity, bool preserveContent = true)
        /// Sets the buffer capacity. If preserveContent is true,
        /// the content of the old buffer is copied over to the
        /// new buffer. The new capacity can be larger or smaller than
        /// the current one; size will be set to the new capacity only if
        /// new capacity is smaller than the current size, otherwise it will
        /// remain intact.
        ///
        /// Buffers only wrapping externally owned storage can not be
        /// resized. If resize is attempted on those, IllegalAccessException
        /// is thrown.
    {
        if (!_ownMem) throw pi::InvalidAccessException("Cannot resize buffer which does not own its storage.");

        if (newCapacity != _capacity)
        {
            T* ptr = 0;
            if (newCapacity > 0)
            {
                ptr = new T[newCapacity];
                if (preserveContent)
                {
                    std::size_t newSz = _used < newCapacity ? _used : newCapacity;
                    std::memcpy(ptr, _ptr, newSz * sizeof(T));
                }
            }
            delete [] _ptr;
            _ptr = ptr;
            _capacity = newCapacity;

            if (newCapacity < _used) _used = newCapacity;
        }
    }

    void assign(const T* buf, std::size_t sz)
        /// Assigns the argument buffer to this buffer.
        /// If necessary, resizes the buffer.
    {
        if (0 == sz) return;
        if (sz > _capacity) resize(sz, false);
        std::memcpy(_ptr, buf, sz * sizeof(T));
        _used = sz;
    }

    void append(const T* buf, std::size_t sz)
        /// Resizes this buffer and appends the argument buffer.
    {
        if (0 == sz) return;
        resize(_used + sz, true);
        std::memcpy(_ptr + _used - sz, buf, sz * sizeof(T));
    }

    void append(T val)
        /// Resizes this buffer by one element and appends the argument value.
    {
        resize(_used + 1, true);
        _ptr[_used - 1] = val;
    }

    void append(const Buffer& buf)
        /// Resizes this buffer and appends the argument buffer.
    {
        append(buf.begin(), buf.size());
    }

    std::size_t capacity() const
        /// Returns the allocated memory size in elements.
    {
        return _capacity;
    }

    std::size_t capacityBytes() const
        /// Returns the allocated memory size in bytes.
    {
        return _capacity * sizeof(T);
    }

    void swap(Buffer& other)
    /// Swaps the buffer with another one.
    {
        using std::swap;

        swap(_ptr, other._ptr);
        swap(_capacity, other._capacity);
        swap(_used, other._used);
    }

    bool operator == (const Buffer& other) const
        /// Compare operator.
    {
        if (this != &other)
        {
            if (_used == other._used)
            {
                if (std::memcmp(_ptr, other._ptr, _used * sizeof(T)) == 0)
                {
                    return true;
                }
            }
            return false;
        }

        return true;
    }

    bool operator != (const Buffer& other) const
        /// Compare operator.
    {
        return !(*this == other);
    }

    void clear()
        /// Sets the contents of the buffer to zero.
    {
        std::memset(_ptr, 0, _used * sizeof(T));
    }

    std::size_t size() const
        /// Returns the used size of the buffer in elements.
    {
        return _used;
    }

    std::size_t sizeBytes() const
        /// Returns the used size of the buffer in bytes.
    {
        return _used * sizeof(T);
    }

    T* begin()
        /// Returns a pointer to the beginning of the buffer.
    {
        return _ptr;
    }

    const T* begin() const
        /// Returns a pointer to the beginning of the buffer.
    {
        return _ptr;
    }

    T* end()
        /// Returns a pointer to end of the buffer.
    {
        return _ptr + _used;
    }

    const T* end() const
        /// Returns a pointer to the end of the buffer.
    {
        return _ptr + _used;
    }

    bool empty() const
        /// Return true if buffer is empty.
    {
        return 0 == _used;
    }

    T& operator [] (std::size_t index)
    {
        pi_assert (index < _used);

        return _ptr[index];
    }

    const T& operator [] (std::size_t index) const
    {
        pi_assert (index < _used);

        return _ptr[index];
    }

private:
    Buffer();

    std::size_t _capacity;
    std::size_t _used;
    T*          _ptr;
    bool        _ownMem;
};


} // namespace pi


#endif // Foundation_Buffer_INCLUDED
